Gearing



Jan. 1946. E. WlLDHABER 2,392,441

- GEARING Filed Aug. 31, 1943 3 Sheeis-Sheet 5 Bnnentor EQNE57' W/LDHABEQ I v v mtorng Patented Jan. 8, 1946 .UNITED STATES PATENT OFFICE GEARING Ernest Wlldhaber, Brighton, N. Y., assignor to Gleason Works, Rochester, N. Y., a corporation of New York Application August 31, 1943, Serial No. 500,671

7 Claims.

i may not be enough traction to move the vehicle.

For this reason, differentials of the .varying leverage type have come into use, especially on trucks and tractors where it is important to provide some means for preventing complete loss of traction when one of the drive wheels of the vehicle slips. In a differential of the varying leverage type, if the tractive power of one wheel is diminished for any reason-the power transmitted to the other wheel is periodically increased. This periodic increase in power is intended to provide enough traction to enable the vehicle to pull itself out of the mud or off of the ice.

Differential gearing of the varying leverage type has heretofore been made in two principal forms. In one form, the teeth of the gears, both of the side gears and the planet pinions, are of special shape, although all of the teeth of each gear are alike and are equally spaced about the axis of the gear. In the other form, the planet pinions are mounted on eccentric axes and the side gears have a lobulate pitch surface, conforming to the eccentricity of the pinions, and their teeth differ from one another progressively around the gears.

The second type of varying leverage differential permits of a large variation of leverage, but the cycle of variation is slower than in the first described type. With the second type, only one cycle of leverage variation takes place per revo-'- lution of a planet pinion, whereas in the first described type, there are as many cycles per revolution of a planet pinion as there are teeth in the pinion. Both types of varying leverage which are subject to severe wear. In the second described type, the side gears have, as stated, a lobulate construction, requiring not only special machinery for cutting the teeth but special machinery to produce the blanks. Moreover, this type is limited to very few ratios of tooth numbers of side gears to planet pinions, for the number of teeth in the side gears must always be a multiple of or the same as the number of teeth in the pinions. Ordinarily, therefore, a two to one ratio is used in the second type.

One object of the present inventionis to pro- I vide varying leverage differential gearing in which the disadvantages of both known types of such gearing may be avoided whileretaining their prime advantages.

Another object of the invention is to provide differential gearing of the varying leverage type which can be out without special machinery and just as fast as standard uniform-motion differential gearing.

A further object of the invention is to provide differential gearing in which the varying leverdifferential gearing require, however, specialv machinery for cutting the teeth, and in both types, moreover, the gear cutting processes are slow as compared with the processes of cutting standard uniform motion differential gears. The first type furthermore is limited to the use of unduly low numbers of teeth in both side gears and pinions and, in addition, the teeth of both side gears and pinions contain profil portions age effect can be obtained without resorting to special designs of gear teeth but in which the gears can have the same tooth shapes as gears of standard uniform-motion differentials.

Another object of the invention is to provide a varying-leverage type differential in which variation in leverage may be obtained by other means than the shape of the gear teeth or the construction of the gears themselves.

In one modification, a further object of the invention is to provide a varying leverage differ.- ential which has the advantages of the second above described form of such differential, namely, large variation in leverage and a cycle per revolution of the planet pinions, but in which these advantages may be realized with gears having standard uniform motion tooth shapes and with gears, also, which are not restricted'as regards the gear ratio employable.

In another modification, still another object of the invention is to provide a varying leverage vdifferential in which gears having teeth of standresent invention, the gears and the pinions used have teeth of the same configuration as the teeth of any ordinary uniform-motion differential and the gears and pinions can be cut on the same machines and in the same way and with the same speed as the gears and pinions of any standard uniform-motion differential. In the differential of the present invention, however, means is provided for rolling the planet pinions-back and forth over the side gears, as they revolve, so that the. pinions will alternately increase and deential housing and that extends in the direction of the axis of the side gears. The hub projection may be in the form of an eccentric or a cam of any suitable shape. When the pinion is rotated, the hub projection travels back and forth in the slot in the differential housing, forcing the pinion The differential itself comprises the two bevel side gears 23, and, in the instance shown, the four planetary bevel pinions 25. The side gears 23 have splined connections with the two axle shafts 21 on which the rear wheels of the vehicle 7 a l are mounted. The side gears 23 are of the same construction as the bevel side gears of a standard, uniform-motion, type differential and they are mounted in the usual manner coaxially of the axis 2i of the axle. They have conical pitch surfaces 3| and 32, respectively, converging in a the pinions are mounted'so that the apices of to roll back and forth about the axis of the side gears of the'differential. Thus, the pinion altemately adds to and subtracts from the rotation of the side gear and thus, the power applied by the side gears to each of. the drive wheels of the vehicle is alternately increased and decreased.

In another embodiment of the invention, the pinion is provided with a square hole and is mounted in the differential housing by means of j a pin that engages in this hole. The portion of tarily and broken away and one of the planet pinions of the differential beingshown in elevation;

Fig. 2 is a section through the differential housing-taken at right angles to the view of Fig. 1 but with the pinion shown in elevation;

Fig. 3 is a section on the line 3--3 of Fig. 2;

their pitch surfaces 31 coincide with the common apex 33. The pinions differ from standard bevel pinions, however, in that instead of being mounted to rotate on shafts coaxial with their geometric axes 36, each is provided with front and rear eccentric hub projections 33 and 39 whose common axis passes through the common apex 33 but is inclined to the geometric axis 36 at an angle A.

The front hub projection 38 of each pinion is mounted in a roller 4i that has a. conical outside surface whose apex coincides with the apex 33. The rear hub projection 39 of each pinion engages in a slot 42 formed in the housing 23 and having Thus, again, power is alstraight parallel sides 43 and 44. The sides 43 and 44 are planes parallel to each other and par- 4 allel to the axis 2| of the difierential housing.

Each conical roller 4| engages in an arcuate slot 45 formed in a spider 46 whose axis coincides with the axis 2! of the differential. This spider a is provided with four equally spaced arms 41 Figs. 4 to 8 inclusive are diagrammatic views illustrating the construction and operation of the embodiment shown in Fig. 12.

In Figs. 1 to 3 inclusive, 20 denotes an automotive differential housing which is mounted in the usual manner for rotation about the axis 2| of the rear axleof the automotive vehicle.

The difierential housing is adapted to be driven in the usual manner to'drive the rear wheels of the vehicle, as through a bevel ,or hypoid pinion meshes with the pinion and which is secured to the differential housing.

not shown and a bevel or hypoid gear 22 which which are secured in suitable slots formed in the two halves of the differential housing 20 and which serve to lock the spider against rotation relative to the differential housing. Each of the arms 41 has a slot 48 extending through it which is shaped to have its sides converging toward a point at the center of the 'slot as shown in Fig. 3. These slots are provided to allow free movement of the pinions without interference from the arms as the pinions rotate and are influenced in their rotation by the eccentric hub projections 33' and 39.

' The slots 45 in which the rollers 4| engage have straight sides 50 and BI which converge to the apex 33' andmatch the sides of the rollers 4i.

The bottom 52 of each slot is an arcuate surface I concentric to the apex 33. Thus, the slots 42 and 45 permit the axes 40 of the hub projections to rock back and forth about the apex 33 in a plane containing the axis 2| of the differential, as the pinions rotate.

The difierential operates in the same way as a standard difierential when the car is moving straight ahead. The pinions 25 will then revolve with the housing 20 without rotating about their axes 36, with the result that the two side gears 23 will be driven at equal speeds and drive'the two axle shafts 21 at equal speeds. When one of the wheels of the vehicle slips, however, and there is unequal traction on the two wheels, the pinions 25 will rotate on their axes 36. Then the shaft projections 39 and conical rollers 4| will act like conical eccentrics or cams. Since these conical eccentrics or cams are constrained by the straight parallel sides of the slots 42 and 45 to move in an axial plane about apex 35 and since the two side gears 28 maintain the axes 55 of the pinions in a plane perpendicular to the axis 2|, the pinions I 25 will themselves tend to move bodily altemately forward and back about the axis 2| of the differential housing so as to move about theaxis 2| alternately withand against the rotation of the housing. Thereby the power applied to each of the side gears 23 will be alternately increased and decreased. In this way, the traction on the wheel, which is not slipping, is periodically varied to assist it to pull the vehicle out o! the mud or snow or oil the ice.

In the embodiment oi the invention shown in Fig. 1 only the forward hub projection 38 of each pinion is mounted irr'a conical roller 4|. It will be understood, however, that the rear hub projections 39 might, also be so mounted if desired.

'In" the extreme positions shown in Fig. 1, the

I instantaneous motion is as it each pinion were turning about the axis '40 of the hub projections. These positions give a maximum difference of the amounts of torque transmitted to the two side gears. Assuming that the frictional loss is zero, the amounts transmitted to the two side gears are in the proportion of spect to the differential housing and with respect to theslot 42 is obtained in known manner as the point oi! intersection of the lines 36-51 and 405| drawn perpendicular to the paths 55 and 56 of points 35 and 40, respectively.

Fig. 6 illustrates the position of the. pinion after the eccentric portion 39 has rotated through an angle of 45 from the position shownin Fig. 5. The center 38 of the pinion is here. at one extreme position of its movement along the line 55. Fig. '1 shows the position of the pinionaiter the eccentric has rotated through an angleof 90 from the position shown in Fig. 6. The direction of travel of the pinion center 35 has been reversed and the center 36 has travelled back to a mean position along the line 55. Fig. 8 shows the position of the pinion after the eccentric has rotated through another angle of 90 from the position shown in Fig. 7. Here the center 55 or the pinion has moved to its other extreme position along the line 55. In its further rotation from the position shown in Fig. 8, the pinion will again reverse the direction of its travel along the line if there are 9 teeth in each of the pinions and 16 teeth'in each of the side gears, and A is equal to 8, the above proportion becomes 1.666. The variation in leverage obtainable, then, with a differential constructed according to the present invention is much more than can be obtained with varying leverage differentials of prior construc-' eccentric hub 39 at diametrically opposite sides with the parallel straight sides 43 and 44 of the slot 42 of the differential housing 20 constrains the hub portion 38 to move back and forth longitudinally in this slot, as described, while the double mesh of the pinion 25 with the side gears 23 prevents the center 36 of the pinion from moving longitudinally of the slot and constrains it to move peripherally along the pitch surfaces 3| and 32 of the side gears, thus imparting motion in opposite directions to the side gears. The eccentric 39 through its engagement with the slot 42, in other words, will move the pinion 25 peripherally relative to the housing 20 as if at any one instant the pinion were turning about the axis 40.

Fig. 5 illustrates a position of the pinion where the eccentric portion 39 has rotated through an angle of 45 from the position shown in Fig. 4. In this rotation, the pinion center 36 has moved peripherally along a line '55 while the center 40 of the eccentric hub portion has moved laterally along the center line 56 of the slot 42. The instantaneous axis 51 of the pinion motion with re- 55 returning to the position shown in Fig. 4*. It

will be seen, therefore, that, as already described,

a cycle of movement of the pinion back and forth peripherally of the side gears .will take place ior each revolution of the pinion, that is, that there will be a cycle of variation in leverage for each revolution of the pinion, to first increase the power applied to each side gear and then decrease it.

Figs. 9 to 11 inclusive illustrate a modification of the invention in which the cycl of variation in leverage occurs a plurality of times in a revolution of a pinion. Here a cam 60, which is of generally triangular shape in cross-section and whose sides are symmetrical with reference to an axis BI, is used instead of an eccentric hub portion. The active surface of this cam is composed of circular arcs, and for convenience in construction, opposite arcs are made concentric to the same center but with different-radii of curvature. 'Thus the arc ab is curved about the same center a: as the are de but the radius of the arc ab is much greater than the radius of the are de. Likewise, the are be is curved about the same center 3/ as the arc ef but with a, much smaller radius and the arc cd is curved about the same center a as th arc fa but with a much greater radius.

The cam 60 is secured to a planet pinion with its center 6| coaxial with the axis of the pinion. The pinion is here denoted by its pitch circle 31' and the two side gears with which it meshes are denoted by their pitch surfaces 3| and 32, respectively. The cam 60 engages in a slot in a diflerential housing which is similar to the slot 42 of th h'ousing 20, and the side walls of this slot are denoted at 43 and 44', respectively. The sides of the cam ,60 are conjugate to the side walls of this slot so as to permit swing of the pinion about the pinion apex.

In the position shown in Fig. 9, the cam portions of and cd which are concentric to the cen-- ter 2 are inengagement with the side walls 43' and 44' of the slot and the center of axis 6| of the pinion is below the center line 62 f the slot.

This is one extreme position of the pinion axis 6!. Fig. 10 shows another positionwhere the pinion has rotated through an angle of 30 from the position shown in Fig. 9. Here the arcs ef the be; which are concentric to the center :1,

are just beginning engagement with the ide walls of the slot. In this position, the pinion has been moved so that its center 8| lies on the center line 82 of the slot. Fig. v11 shows a position after the pinion has been turnedfurther through an angle of 30 from the position shown in Fig. 10. Here the arcuate portions, which are curved about the center 11 are still in engagement with the side walls of the slot but the axis 6| of the pinion has moved to a position above the mean center line 82 of the slot. This is the other extreme position or the pinion axis' and is half a cycle dlflerent from the position shown in Fig. 9. In this embodiment of the invention, then, there are three cycles of variation in leverage for each revolution of the planet pinion.

A further embodiment of the invention is illustrated in Figs. 12 to 16 inclusive which show specifically a two pinion diilerential. The differential housng is denoted at 19. It is formed with a flange 89 against which the rear axle drive gear (not shown) is secured. The bevel side gears of the differential are denoted at H and the bevel planet pinions at 12. Both gears and pinions are again of standard construction, each having teeth of uniform shape, uniformly spaced about their respective axes. The side gears are mounted coaxially to rotate about the axis 13 oi the differential housing. The pinions 12 are also mounted coaxially but instead or being broached with round'holes in the conventional manner,

they are broached with squar holes 14 (Figs. 13

to 16 inclusive). The square hole in each pinion is adapted to receive a cam-shaped portion I8 of a pin 15. The pin carries a spaced block 11 that serves to hold the pinions and side gears in place. the differential housing 19. This may be done by making the pin square, except for its cam portions 16, and breaching square holes in th differential housing to receive the pin.

If the portions of the pin 15, which engage in the square holes or the pinions I2, .were of cylindrical shape as indicated in dotted-lines at 18 in Fig. 13, and the axis 19 of these cylindrical portions coincidedwith the axes of the pinions themselves, then the pinions would simply turn about the axis 19 as the pinions revolved. Sinc the portions ,18 of the pin, which engage in the square holes I! of the pinions, depart from cylindrical The piri'is secured against rotation in a,so2,441

enveloped by said plane sides during the given relative motion between pinion and pin. Their shape can be determined by layout or by comthe arcs of portion 82-83 are centered at 88 and 89, respectively, while the central portion or the surface 82-83 is a circular arc whose center is at 99. Likewise, adjacent points 84 and 85, the

shape, as clearly shown in Fig. 13, the pinions will -be displaced bodily back and forth about the axis I8 01 the difierential as the pinions revolve; It is this back and forth bodily displacement which produces the varying leverage effect.

In the form of pin 15 shown, each portion 16 is so shaped as to contact with all four sides of a square hole 14 in a pinion 12. Thus in Fig. 13 contact is made at points 82, 83, 84, and on the normals 88 and 8| to the sides of the square hole. Near the points 82 and 83, the profile of the cam portion 18 of the pin is more curved than the circle 18 but midway between the points 82 and 83the profile of the pin portion 18 is less curved than the circle; Diametrically opposite portion 84-85 of the pin is less curved than the circle 18 adjacent to the points 84 and 85 and more curved midway between these points.

Once the portions 82-83 and 84-85 have been established, the motion of the axis I9 01 the pinion in a peripheral'direction along the line 8I in'a plane perpendicular to the axis I3 is determined. If continuous contact with all four sides-oi the square hole 14 is desired, the portions 85-82 and 88-84 of the pin. profile are made conjugate to the plane sides of the hole, that is, they are madeof such shape as may be arcs of the portion 84-85 are centered at 88 and 89, respectively, and .the middle of this portion is centered at 90. The invention is not limited, however, to the employment of pin portions which are made up of circular arcs.

Fig. 14 shows the relative positions of the hole "and pin portion 18 after the pinion 12 has rotated through an angle of 22 /2" from the position shown in Fig. 13. In this figure, the contact shifts from one circular arc to another clrcular are centered at 88 and 90, respectively. The

connecting line 92 between the two centers 88 and is then the normal at the points of contact 93 and 94. The instantaneous center of relative motion of the pinions with respect to the pin 15 must lie on this normal and inasmuch as the axis 19 of the pinion moves along the line 81, said instantaneous center must also lie on a line 19-95. It is the intersection 95 of the lines 93 and 19-95, which are normal to the points of contact and to the line of travel of the axis of the pinions, respectively. At the considered moment, the pinion moves as if turning about an eccentric axis passing through the point 95 and the apex 96 (Fig. 12) of the pinion.

Fig. 15 shows a further position of the parts after the pinion has rotated through an angle of 22%" from the position shown in Fig. 14, and

Fig. 16 shows the position where the pinion has rotated through an angle or 22 /2 from the position shown in Fig. 15. After another 22 /z of rotation of the pinion, the position of the parts would be similar to that shown in Fig. 13 with the exception that the square hole 14 would have been rotated through 90f.

In the position shown in Fig. 14 and in the position symmetrical thereto which is shown in Fig. 16, the instantaneous center of motion 95 has amaximum distance from the axis 19 of the pinion and gives the maximum variationot leverage. In Fig. 15,

the axis 19 has a maximum distance from the center 9| about which, the arc centers 88, 89, and

95 are spaced.

Theembodiment of the invention shown in Figs. 12 to 16' inclusive is particularly suited for passenger cars. It will produce'four cycles of. variation in leverage per revolution of a planet pinion. The square holes through the pinions and through the difierential housing 19 can be broached and may be burnished at about the same cost as. the round holes on a standard differential. The pin 15 can also be broached and 4 further modification and this application is intended to cover any variations, uses or adaptations of the invention following, in general, the

principles of the invention and including such departures from the present disclosure as come within known or customary practice in the gear art and as may be applied to the essential feaclaim is: 1

1. A differential mechanism comprising a rotatable housing, a pair of side gears journaled in said housing for rotation about the axis of the housing, pinions meshing with said side gears and disposed in said housing to rotate therewith,

and means constraining each pinion to move back and forth relatively about the axis of the side gears as the pinion rotates on its axis comprising a guide slot and a control member movable therein, one of which is fixed relative to said housing and the other of which is fixed relative to the pinion, said control member being noncircular in cross-section and being of different cross-sectional shape from said slot.

2. A differential mechanism comprising a ro tatable housing, a pair of side gears journaled in said housing for rotation about the axis of the housing, pinions meshing with said side gears anddisposed in said housing to rotate therewith, and means constraining each pinion to move back and forth relatively about the axis of the side gears as the pinion rotates on its axis comprising a plane-sided slot and a non-circular cam-shaped control member which is movable therein, one of which is fixed relative to the housing and the other of which is fixed relative to the pinion, said control member being of different cross-sectional shape from said slot.

3. A differential mechanism comprising a rotatable housing, a pair of bevel side gears journaled in said housing for rotation about the axis of said housing, a bevel pinion mounted in said housing to rotate therewith and meshing with the two side gears, said side gears having umiormly shaped teeth, uniformly spaced about their axis and said pinion having uniformly shaped teeth, uniformly spaced about its axis, said pinnon-circular cross-section and of different crossslot formed therein in which said projection engages and'which is of difierentcross-sectional shape from said projection, said slot having parallel sides and the center line of said slot lying in the same plane with the axis of the side gears.

4. A differential mechanism comprising a rotatable housing, a pair'of bevel side gears journaled in said housing for rotation about the axis of the housing, a bevel pinion mounted in said housing to rotatetherewith and meshing with the two side gears, said pinion having a bore therethrough, and a pin secured to said housin and having a non-circular cam-shaped portion engaging in the bore of the pinion.

5. A difierential mechanism comprising a rotatable housing, a pair of bevel side gears journaled in said housing for rotation about the axis of the housing, a bevel pinion mounted in said housing to rotate therewith and meshing with the two side gears, said pinion having a noncircular bore therethrough, and a pin. secured to said housing and having a cam-shaped portion engaging in the bore of the pinion which is of different cross-sectional shape from the cross-- sectional shape of said bore.

6. A differential mechanism comprising a rotatable housing, a pair of bevel side gears Journaled in said housing for rotation about the axis of the housing, a bevel pinion mounted in said housing to rotate therewith and meshing with the two side gears, said pinion having a planesided bore therethrough and a pin secured to said housing and having a portion, which is of sectional shape from said bore, engaging in said bore. I

7. A differential mechanism comprising a rotatable housing, a pai of bevel side gears journaled in said housing for rotation about the axis oi? the housing, a bevel pinion mounted in said housing to rotate therewith and meshing with the two side gears, said pinion having a square hole therethrough and a pin secured to said housing and having a portion, which is of non-circular cross-section and of difi'erent cross-sectional shape from said bore, engaging in said bore.

ERNEST WILDHABER, 

